Whereas the revelation of firewalls is a breakthrough—it revealed a problem no one realized was there, and has forced scientists to rethink some of the progress that appeared to have been made in resolving a fundamental conflict in physics—the incompatibility of general relativity that describes the universe on a grand scale and quantum mechanics, which applies to the subatomic world. Both theories are needed to address tiny, yet massive black holes, but the two theories cannot currently work together.
In 1997 Juan Maldacena of the Institute for Advanced Study in Princeton, N.J., found a way to reconcile some aspects of the conflicting theories and formulate a version of quantum gravity that could describe black holes. His work was a major step forward but the firewall theory shows that Maldacena’s advance didn’t solve as many problems as was assumed at the time. “People had lulled themselves to sleep” thinking certain black hole dilemmas had been resolved, says Columbia physicist and mathematician Peter Woit. “This has shaken people out of their dogmatic slumber and they’re realizing, ‘Wait a minute, we don’t really understand this.’” Marolf agrees: “It forces us to reconsider issues that we thought were settled,” he says. “It’s definitely dismaying to see how far we still have to go.”
How to move forward now is less than clear, however. “I think it’s fair to say quantum gravity is stuck,” says Matt Strassler, a visiting physicist at Harvard University. “It’s not obvious that any big progress is being made at the moment.” Not to worry, though—there’s nothing physicists love more than a challenge. “I think we have a long way conceptually to go,” Stanford University physicist Leonard Susskind said earlier this month during a Google+ Hangout on the topic of firewalls hosted by the Kavli Institute. “I think there’s a large gap in our understanding. We’ll fill it though. Rest assured, we’ll get it.”